The present invention relates to gas-generating compositions, more specifically to gas-generating compositions that are filled in an air bag system that expands an air bag of a vehicle passenger-protecting apparatus, or a pretensioner device that takes up a seat belt.
The major components of the gas-generating compositions used in the conventional airbag systems are sodium azide and various oxidants. However, because sodium azide is toxic and difficult to handle, gas-generating compositions without sodium azide were needed.
Preferable gas-generating compositions may: not degrade naturally; be resistant to environmental changes at ambient temperature; have appropriate burning rate; generate a large amount of gas without generating carbon monoxide and combustion residue; and be inexpensive. In order to obtain preferable gas-generating compositions, gas-generating compositions that include ammonium nitrate as the major component have been developed. For example, Japanese Patent Application Laid-Open No. Hei 10-59792 discloses a gas-generating composition consisting of an oxygen-containing binder and ammonium nitrate. Also, Japanese Patent Application Laid-Open No. 2000-103691 discloses a gas-generating composition consisting of a macromolecular compound such as polyacrylic macromolecular compound, polyacetal, urea resin, melamine resin, ketone resin and cellulose macromolecular compound, and ammonium nitrate or phase-stabilized ammonium nitrate.
However, the performance could change in the conventional gas-generating compositions, due to ambient changes, such as temperature changes, received while loaded on the vehicles. In other words, the stability of the conventional gas-generating compositions against ambient changes was relatively low.
An object of the present invention is to provide gas-generating compositions having improved stability against ambient changes.
To achieve the above object, the present invention provides a gas-generating composition including ammonium nitrate, an organic binder, and a stabilizer for stabilizing the gas-generating composition. The stabilizer consists of at least one nitrogen-containing compound having a nitrogen atom with an unpaired electron.
Another aspect of the present invention provides a gas-generating composition grain having a length and a radial dimension. The gas-generating composition grain contains ammonium nitrate, an organic binder, and a stabilizer for stabilizing the gas-generating composition. The stabilizer consists of at least one nitrogen-containing compound including a nitrogen atom with an unpaired electron. The minimum value among the length and the radial dimension is between 0.1 and 7 mm.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.